#!/bin/bash
#
# turn a noarch package into srpm that "builds" into it again,
# but without the actual build process -- effectively to get rid
# of the need for BuildRequires during bootstraps; typical use:
# $ rpm -bs --nodeps $(renoarch this.noarch.rpm)
# (--define '_sourcedir /path/to/noarch/RPMS' might be useful too)
#
# NB: scripts/triggers not carried over [so far]

[ -s "$1" ] || exit 1

# mark those; mandates release bump afterwards (NB: .re > .1)
SUF=".re"

q() { rpm -qp --qf="$1" "$2"; }

mkspec() {

rpm -qp "$1" >&/dev/null || exit 2

OUT="$(basename "$1")"
OUT="${OUT%.rpm}.spec"

export LANG=C.UTF-8

read N V R < <(q '%{name}\t%{version}\t%{release}\n' "$1")
read E < <(q '%{epoch}\n' "$1"); E="${E/(none)/}"
read S < <(q '%{summary}\n' "$1")
read L < <(q '%{license}\n' "$1")
#read G < <(q '%{group}\n' "$1")	# unused
#read D < <(q '%{description}\n' "$1")	# unused

P="$(rpm --eval '%packager')"
P="${P/\%packager/Renoar C.H. <renoarch@localhost>}"

{
cat << EOF
# bootstrap spec generated by $(basename "$0") on $(date +%Y-%m-%d)

Name: $N
Version: $V
Release: $R$SUF
EOF

[ -z "$E" ] ||
cat << EOF
Epoch: $E
EOF

cat << EOF

Summary: piggyback the needed %name version
License: $L
Group: Development/Other

Source: $(basename "$1")
BuildArch: noarch
AutoReqProv: no

EOF

{
rpm -qp --requires "$1" |
	grep -v '^rpmlib' |
	sed 's,^,Requires: ,'
echo

rpm -qp --provides "$1" |
	sed 's,^,Provides: ,'
} | sed 's,:[^ ].*$,,' # drop disttag

[ -z "$SUF" ] ||
cat << EOF
Provides: $N = ${E:+$E:}$V-$R
EOF

cat << EOF

%description
%summary

%prep
%setup -cT
rpm2cpio %SOURCE0 | cpio -id

%build
# any "corrective" action here

%install
cp -a . %buildroot

%files
EOF

rpm -qlp "$1" | grep -v "^("

cat << EOF

%changelog
* $(date '+%a %b %d %Y') $P ${E:+$E:}$V-$R$SUF
- bootstrap package

EOF
} > "$OUT" && echo "$OUT" || rm "$OUT"

} # repackage

for i in "$@"; do mkspec "$i"; done